Stratospheric black carbon injections and climate variability

• Main Author: Coupe, Joshua
• Format: Text
• Language: unknown
• Published: No Publisher Supplied 2020
• Subjects: Arctic; black carbon
• Online Access: https://dx.doi.org/10.7282/t3-0yz7-zj75; https://rucore.libraries.rutgers.edu/rutgers-lib/65067/

The climate impacts of smoke from fires ignited by nuclear war would include global cooling and crop failure. Previous efforts to model the climate impact of nuclear war have used a simplified representation of the aerosols that would be generated by massive fire storms. Here, I examine six nuclear war scenario simulations using an Earth system model that includes the growth of black carbon aerosols for the first time. I show that including aerosol growth processes reduces the residence time of soot aerosols, but the magnitude of global climate impacts are not reduced and a “nuclear winter” can be expected following a nuclear war scenario where 150 Tg of soot is injected into the upper troposphere and lower stratosphere. I show an El Niño-like response is robust across all nuclear war simulations for up to seven years. I employ sensitivity tests with the same climate model to understand the mechanisms behind the response, showing that the cooling of the Maritime Continent, cooling of tropical Africa, and the equatorward shift of the Intertropical Convergence Zone can all contribute to the El Niño-like state. Finally, I investigate the response of the Northern Hemisphere wintertime circulation to soot aerosol injection through variations to the stratospheric polar vortex and surface Arctic Oscillation response. I conduct another sensitivity experiment to isolate the role of a tropospheric and stratospheric pathway for stratospheric polar vortex strengthening. I show that surface cooling can cause an acceleration of the Northern Hemisphere wintertime stratospheric polar vortex that is statistically significant compared to the non-perturbed climatology, but which is only a fraction of what occurs in a model simulation that includes aerosol heating. The dynamics responsible for influencing the modes of climate variability examined here are applicable for the response to volcanic eruptions, asteroid impact events, and geoengineering experiments involving stratospheric aerosols.